Maekawa and colleagues studied a rat-canine chimeric anti-PD-L1 mAb (c4G12) in dogs with oral malignant melanoma (OMM) and undifferentiated sarcoma, and Igase and colleagues studied rat-canine-chimeric (ch-4F12-E6) and caninized anti-PD-1 (ca-4F12-E6) antibodies in dogs with OMM as well as other spontaneous tumors including squamous cell tumors and cutaneous melanoma (30, 32). The gene discussed is PDCD1; the disease is cutaneous melanoma.